Drainage Investigations

Drainage Investigations are for non-urgent sites that cannot be resolved by maintenance.

When an issue cannot be resolved by maintenance SPU staff will make a referral, but customers can also request an investigation. 

If a Drainage Investigation finds that something in the public right-of-way is causing the issue, SPU’s next steps may be a near-, mid- or long-term solutions. In some cases, the issue may require expensive and/or complex solutions that will take years or decades to resolve.

Submit a Drainage Issue Report

Use the Drainage Issue Report Form to request a drainage investigation.

Email SPUDWW_Investigations@seattle.gov if you prefer to receive a PDF of the form to complete.

Drainage Investigation Process

Drainage Investigations may take months. Once a complete Drainage Issue Report Form is submitted, SPU will:

1. Contact the customer for more information:
   1. Impacts to private property
   2. Dates and frequency of events
   3. Photos and videos of the issue
   4. Site history and ownership
2. Research and investigate:
   1. SPU infrastructure and work history
   2. Recent site changes in the area (permits, projects, etc.)
   3. Ownership of onsite and nearby drainage assets.
3. Conduct site visit(s) during wet and/or dry weather
4. Complete a technical assessment: This is a basic engineering assessment of potential site solutions. It determines the scale and general costs of potential solutions.
5. Complete a risk assessment: Assign a risk assessment score to the site.
6. Communicate finding to the customer: Drainage Investigations will notify the customer of the outcome.
   1. If SPU determines it is a private property issue, SPU will notify the customer. In some cases, property owners have caused the issue through unpermitted work or damage caused to a public drainage system. In these cases, SPU may pursue enforcement against the owner under any applicable section of the Stormwater Code or Side Sewer Code (SMC 22.800 & SMC 21.16 respectively) to require resolution. 

Resolving Public Drainage Issues

If a Drainage Investigation determines that a site 1) has no or little impact to private or City property or SPU assets, and 2) is unlikely to impact to public safety, it will be documented as a drainage issue site but will not be prioritized for investment.

If a Drainage Investigation finds a higher risk assessment scores, it will receive further engineering analysis. They will determine what options are feasible. Lower complexity sites can often be resolved more quickly:

• Low complexity sites: These sites require limited engineering design, can be constructed or installed by City crews, and have a relatively low-cost solution like an asphalt berm or adding a drainage structure.
• Moderate-complexity sites: These sites require extensive design and planning to install new drainage systems or drainage system extensions. They must be sequenced and prioritized for available resources as part of SPU’s planning and capital improvement work. A limited number of projects are prioritized each year.
• High complexity sites: These sites are part of large drainage system challenges that need to be addressed through expensive and complex  neighborhood-scale solutions. They must be sequenced and prioritized for available resources as part of SPU’s planning and capital improvement work. A limited number of projects are prioritized each year.  

See our Current Projects page for a list of currently prioritized capital projects.

To learn more about drainage and wastewater planning see our Drainage & Sewer Plans page.